Synthesis and Structure of Bi<SUB>3</SUB>NF<SUB>6</SUB>: A Member with n = 3 of the Vernier Phases M<SUB>n</SUB>X<SUB>2n+1</SUB>

Heating of NH₄BiF₄ at 285°C under dry ammonia yields Bi₃NF₆ via the intermediate products NH₄Bi₃F₁₀ and BiF₃. Bi₃NF₆ is an air-sensitive grey powder decomposing under dry NH₃ at 350°C to form Bi metal. It crystallizes in the orthorhombic space group Pbcm, with a = 581.74(2), b = 570.18(2), c = 1851.13(5) pm, Z = 4. The structure was determined by X-ray and neutron powder diffraction data. Bi₃NF₆ belongs to the family of vernier phases M_nX_2n+1, and represents the first member of the series with n = 3. The two-symmetry independent Bi atoms exhibit coordination numbers of eight. Copyright 1995, 1999 Academic Press